1. Field of the Invention
The present invention is generally related to an automatic calibration and optimization method for multiple drive marine propulsion systems and, more particularly, to a procedure that is intended to properly align the propeller shafts of the multiple drive system in such a way that the efficiency of fuel usage is maximized.
2. Description of the Related Art
Many types of known propulsion systems utilize multiple drive units to propel a marine vessel. The multiple drive units can comprise outboard motors, sterndrive units, or pod drive systems. The pod drive marine propulsion systems are most likely to benefit from the automatic calibration system of the preferred embodiments of the present invention. Although the basic concepts of the present invention can be applied to other types of marine propulsion systems, it will be described herein in conjunction with multiple drive units that are supported below the hull of a marine vessel in the manner generally described in U.S. Pat. Nos. 7,131,385 and 7,267,068. This same type of marine propulsion system is also described in U.S. Pat. Nos. 7,305,928 and 7,387,556.
When two or more marine drive units are used to propel a marine vessel, the net total thrust vector exerted on the marine vessel is the resultant of the individual thrusts provided by the multiple drive units. As a result, it is possible to exert a thrust which propels the marine vessel in a generally straight direction even though neither of the two drive units is aligned in a parallel relationship with the centerline of the marine vessel (e.g. its keel line). This occurs because two drives whose propeller shaft axes are not parallel to the keel of the marine vessel can add together, vectorally, to result in a combined thrust that is parallel to the keel line. Although this situation propels the marine vessel in a forward direction which parallel to its keel, it does so in a less than efficient manner in most cases. One of the purposes of the preferred embodiments of the present invention is to align the individual drive units so that the efficiency of their operation can be improved. One of the basic purposes of the preferred embodiments of the present invention is to position the individual drive units of the multiple drive propulsion system so that they not only result in a combined thrust that drives the marine vessel in a generally straight and consistent direction but, in addition, also minimize the fuel usage required to propel the boat.
Although the preferred embodiments of the present invention are not known to those skilled in the art, various other marine propulsion systems and steering mechanisms are known and are discussed below.
U.S. Pat. No. 3,899,992, which issued to Fuller on Aug. 19, 1975, describes a marine steering device. A propeller duct or nozzle provided with controllable passageways and modulated for the purposes of developing a controllable athwartship thrust which may be used without rudder deflection or drag arising therefrom for the purpose of making minor directional changes necessary to keep a ship on course, and when used in conjunction with a rudder, to increase steering effectiveness at high and full helm angles, with possible reduction in rudder area is described. The steering device also improves effectiveness when going astern or when maneuvering alongside with a stopped ship. The device retains the improved propulsive efficiency characteristic of a ducted propeller whilst compensating for the increase in wetted area represented by the duct or nozzle.
U.S. Pat. No. 3,972,224, which issued to Ingram on Aug. 3, 1976, describes a shaft efficiency monitoring system. It continuously provides direct readouts of horsepower and efficiency of a rotating shaft. It includes a husk assembly associated with the shaft and providing electrical signals proportional to shaft torque. It comprises a tachometer for providing electrical signals proportional to shaft rotational speed, electrical circuitry for electronically multiplying the torque signals by the RPM signals to determine shaft horsepower, and a dividing network for dividing the shaft horsepower signal into an electrical signal representing the rate of fuel consumption to provide a continuous indication of instantaneous system efficiency.
U.S. Pat. No. 4,939,660, which issued to Newman et al. on Jul. 3, 1990, discloses a fuel conserving crew system for a marine drive unit. It discloses a system for optimizing the operating efficiency of a boat by balancing fuel consumption against cruising speed and utilizes a comparison between engine speed and boat speed to effect automatic positioning of the drive unit.
U.S. Pat. No. 5,785,562, which issued to Nestvall on Jul. 28, 1998, describes a method for trimming of a boat propeller shaft and drive unit with means for performing the method. It comprises an internal combustion engine and an outboard drive driven by the engine. The engine has an engine control unit which holds the speed of the engine constant independently of the load on the engine. A flow meter continuously gives a signal, which represents the instantaneous fuel consumption to the engine control unit. A trim control unit controls the trim angle of the drive so that the lowest fuel consumption for the set engine speed is achieved.
U.S. Pat. No. 5,910,032, which issued to Gruenwald et al. on Jun. 8, 1999, discloses a marine propulsion system, incorporating a jet pump, which provides improved mass flow through the pump by utilizing an inlet opening which initially diverges to a transition point in front of an impeller and then diverges from the transition point past the impeller region to the outlet opening of the pump. Significantly increased flow rates per horsepower are achieved by reducing the normal restrictions caused by the inlet and outlet openings of known pumps.
U.S. Pat. No. 6,234,853, which issued to Lanyi et al. on May 22, 2001, discloses a simplified docking method and apparatus for a multiple engine marine vessel. The docking system is provided which utilizes the marine propulsion unit of a marine vessel, under the control of an engine control unit that receives command signals from a joystick or push button device, to respond to a maneuver command from the marine operator. The docking system does not require additional propulsion devices other than those normally used to operate the marine vessel under normal conditions.
U.S. Pat. No. 6,458,003, which issued to Krueger on Oct. 1, 2002, describes a dynamic trim of a marine propulsion system. It defines a program to control the trim position of a propulsion unit mounted on a watercraft for a desired utility mode. Also, a method and system for controlling the trim position in a given utility mode by using the defined program is described. In defining the program, a first utility mode is defined and the watercraft is operated in the defined mode as a normal operation. Multiple trim positions are selected throughout the course of operation in the defined mode.
U.S. Pat. No. 6,885,919, which issued to Wyant et al. on Apr. 26, 2005, discloses a method for controlling the operation of a marine vessel. A process is provided by which the operator of a marine vessel can invoke the operation of a computer program that investigates various alternatives that can improve the range of the marine vessel. The distance between the current location of the marine vessel and a current way point is determined and compared to a range of the marine vessel which is determined as a function of available fuel, vessel speed, fuel usage rate, and an engine speed. The computer program investigates the results that would be achieved, theoretically, from a change in engine speed. Both increases and decreases in engine speed are reviewed and additional theoretical ranges are calculated as a function of those new engine speeds.
U.S. Pat. No. 6,997,763, which issued to Kaji on Feb. 14, 2006, describes a running control device. It controls propulsion force and tilt angle of a propulsion device relative to the hull of the watercraft. The running control device also sets an optimum trim angle automatically. The running control device includes a propulsion force control section that controls the propulsion force of the propulsion device. The running control device also includes a tilt angle control section that controls the tilt angle of the propulsion device.
U.S. Pat. No. 7,066,775, which issued to Seter on Jun. 27, 2006, describes a propeller wash straitening device. It is intended for increasing the efficiency of propeller driven watercraft. An elongated outer tubular member open at each end thereof is adapted for connection to the boat or vessel to position the outer member immediately downstream of the propeller and in substantially longitudinal fixed alignment with the direction of axial thrust produced by the propeller. A plurality of elongated hollow open-ended inner tubular members is positioned in closely packed fashion within and generally co-extensive with a substantial portion of the length of the outer tubular member.
U.S. Pat. No. 7,131,385, which issued to Ehlers et al. on Nov. 7, 2006, discloses a method for braking a vessel with two marine propulsion devices. A method for controlling the movement of a marine vessel comprises steps that rotate two marine propulsion devices about their respective axes in order to increase the hydrodynamic resistance of the marine propulsion devices as they move through the water with the marine vessel. This increased resistance exerts a braking thrust on the marine vessel. Various techniques and procedures can be used to determine the absolute magnitudes of the angular magnitudes by which the marine propulsion devices are rotated.
U.S. Pat. No. 7,220,157, which issued to Pettersson on May 22, 2007, describes an arrangement and method for parallel alignment of propeller shafts and means for propeller alignment. An arrangement and method for parallel alignment of propeller shafts in a first and a second underwater housing arranged on the hull of a vessel, which are arranged to rotate around an axis of rotation which is angled in relation to the propeller shafts arranged in each underwater housing, which arrangement includes a servo motor arranged for each underwater housing, which servo motor is arranged to rotate the underwater housing is disclosed. A position sensor arranged for each servo motor, which position sensor is arranged to detect an angular position of the underwater housing is also described. A control unit in which a reference angular position of the underwater housing is arranged to be stored during a calibration of the position of the underwater housing and a calibrator of the position of the underwater housings by storing output signals from the position sensors in the control unit during a parallel alignment of propeller shafts in two underwater housings are arranged on the hull of a vessel.
U.S. Pat. No. 7,267,068, which issued to Bradley et al. on Sep. 11, 2007, discloses a method for maneuvering a marine vessel in response to a manually operable control device. A marine vessel is maneuvered by independently rotating first and second marine propulsion devices about their respective steering axes in response to commands received from a manually operable control device, such as a joystick. The marine propulsion devices are aligned with their thrust vectors intersecting at a point on a centerline of the marine vessel and, when no rotational movement is commanded, at the center of gravity of the marine vessel.
U.S. Pat. No. 7,305,928, which issued to Bradley et al. on Dec. 11, 2007, discloses a method for positioning a marine vessel. A vessel positioning system maneuvers a marine vessel in such a way that the vessel maintains its global position and heading in accordance with a desired position and heading selected by the operator of the marine vessel. When used in conjunction with a joystick, the operator of the marine vessel can place the system in a station keeping enabled mode and the system then maintains the desired position obtained upon the initial change in the joystick from an active mode to an inactive mode.
U.S. Pat. No. 7,387,556, which issued to Davis on Jun. 17, 2008, discloses an exhaust system for a marine propulsion device having a driveshaft extending vertically through a bottom portion of a boat hull. An exhaust system for a marine propulsion device directs a flow of exhaust gas from an engine located within the marine vessel, and preferably within a bilge portion of the marine vessel, through a housing which is rotatable and supported below the marine vessel. The exhaust passageway extends through an interface between stationary and rotatable portions of the marine propulsion device, through a cavity formed in the housing, and outwardly through hubs of pusher propellers to conduct the exhaust gas away from the propellers without causing a deleterious condition referred to as ventilation.
U.S. Pat. No. 7,389,165, which issued to Kaji on Jun. 17, 2008, describes an attitude angle control apparatus, attitude angle control method, attitude angle control apparatus control program, and marine vessel navigation control apparatus. The program selects an optimum attitude angle in a short period of time without being affected by disturbances at sea by measuring attitude angles and specific fuel consumption during navigation for any combination of a hull and propeller, create a statistical model based on the measured data, and select an optimum attitude angle on the statistical model. A marine vessel navigation control apparatus includes a control speed navigation controller and a trim angle controller. The trim angle controller includes an evaluated-value calculation module which calculates evaluated values of the trim angle, a storage medium, a statistical model creation module which creates statistical models using the evaluated values stored in the storage medium as an explained variable, and predetermined information including the trim angle as an explanatory variable, and a target trim angle calculation module which calculates a target trim angle based on the statistical model.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
When the combined thrusts of two or more marine propulsion drives are used to propel a marine vessel, it is beneficial to assure that the propeller shafts of the multiple drive units are aligned with each other and with a line that is generally parallel to the keel line of the marine vessel. By assuring this physical relationship, proper operation of the marine propulsion device can be improved. It would therefore be beneficial if an automatic calibration system could be provided which positions the marine drives in such a way that the improved operation of the marine vessel is achieved and the fuel usage of the marine vessel is reduced.